Corrugated paperboard comprises a fluted medium and a linerboard adhesively joined to the tips of the fluted medium on one or both sides thereof. The corrugated paperboard is then cut into sections or into blanks for storage and scored to form containers for shipment of goods.
Various attempts have been made to produce corrugated board having improved wet stiffness properties by impregnating the medium prior to corrugation and assembly of the corrugated board. Likewise, attempts have included resin impregnation of the assembled corrugated board. For example, U.S. Pat. No. 3,823,028 to Arian et al involves pouring liquid impregnating resins into the open ends of finished corrugated boards and allowing the resins to drain out the other side's open ends. Other attempts have been made to employ in-line methods of resin treatment of the board after corrugation, but prior to assembly, as shown in U.S. Pat. No. 3,936,339.
Other processes have not been satisfactory because of the difficulty in producing a uniformly resin-impregnated corrugated medium if resin impregnation is attempted after corrugation. If resin impregnation of medium is performed prior to fluting the impregnated medium, the medium sticks to the corrugating rolls and board cracking is encountered during manufacture of the board.